The present invention relates to a semiconductor device using a gallium nitride-based compound semiconductor and a manufacturing technique for the same and, more particularly, to a gallium nitride-based compound semiconductor laser, a method of manufacturing the same, and a method of manufacturing a gallium nitride-based compound semiconductor device.
In recent years, gallium nitride-based compound semiconductors such as GaN, InGaN, GaAlN, and InGaAlN have received a great deal of attention as materials for blue semiconductor lasers. Semiconductor lasers using these materials are designed as short-wavelength lasers and hence can focus beams to small diameters. Owing to this advantage, these lasers are expected to be used as light sources for high-density information processing such as processing in optical disks.
Various structures and manufacturing methods have been proposed for semiconductor lasers of this type. In either of these proposed techniques, a laser having satisfactory characteristics has not been obtained because a gallium nitride-based compound semiconductor layer is difficult to cause crystal growth. That is, even if a gallium nitride-based compound semiconductor layer is formed by crystal growth, a high-quality crystal cannot be obtained. Since the crystal quality is poor, carriers cannot be efficiently injected into the active layer. In addition, in a structure having a striped opening in a current blocking layer, the crystal quality of the regrown layer formed after etching for forming the striped opening deteriorates, resulting in voltage drops at the electrode contacts and the like.
To realize a highly reliable blue semiconductor laser which is used for optical disks and the like and operates at a low threshold and a low voltage, it is important to efficiently inject carriers into the active layer and suppress voltage drops at the electrode contacts and the like. However, with the prior techniques, these requirements cannot be satisfied.
According to a semiconductor laser using a gallium nitride-based compound semiconductor material, it is difficult to cause crystal growth of the material and to obtain a high-quality crystal layer. In addition, the crystal quality of the regrown layer formed after etching for forming a striped opening deteriorates. For these reasons, carriers cannot be efficiently injected into the active layer, and voltage drops occur at the electrode contacts and the like. That is, it is difficult to realize a highly reliable device which is used for optical disks and the like and operates at a low threshold and a low voltage.
That a gallium nitride-based compound semiconductor layer cannot be satisfactorily regrown after it is etched applies to various semiconductor devices using gallium nitride-based compound semiconductors as well as semiconductor lasers.